Start64!USBDLM is a Windows service that gives control over Window's drive letter assignment for USB drives. Running as service makes it independent of the logged on user's privileges, so there is no need to give the users the privilege to change drive letters.

It automatically solves conflicts between USB drives and network or subst drives of the currently logged on user. Furthermore you can define new default letters for USB drives and much more.

USBDLM works with Windows 2000, XP, Server 2003, Vista, Windows 7 and Server 2008. The x64 version works on x64 editions of Windows only.


It is tested under

  • Windows 2000 SP4 + Rollup 1
  • Windows XP SP2
  • Windows XP SP3
  • Windows XP x64 SP1
  • Windows 2003 Server SP1
  • Windows Vista Business SP2
  • Windows Vista Ultimate x64 SP2
  • Windows 7 Ultimate x64
  • Windows 2008 Server R2 x64

When a removable drive (USB flash drive, flash card reader, portable hard drive) is attached for the first time, Windows mounts it to the first available drive letter. If there is a network share on this letter, then Windows XP-SP2 will use it anyway for the new USB drive because since XP network shares are specific to the current user and not visible in the context of the system where the letter is assigned. The USB drive then appears to be invisible.

You can change the letter assignments in the Windows Disk Management Console with a lot of mouse clicks but you have to do it again for every new device.

And, for USB devices that have no serial number you have to do it too when you attach it to a different USB port.


With USBDLM you can

  • check if the letter is used by a network share of the currently logged on user and assign the next letter that is really available (no configuration required)
  • reserve letters, so they are not used for local drives
  • assign a letter from a list of new default letters, also dependend on many different criteria as the active user, drive type, type of connection (USB, FireWire), USB port, volume label, size, user and others
  • let remove the drive letters of card readers as long as there is no media present
  • ask the user for a password before he can use a drive
  • let show an balloontip on drive arrival which shows the assigned drive letter
  • executing an autorun, also depending on the criterions mentioned above
  • and much more...

USB Drive Letter Manager